Authorities found the remnants of a small homemade bomb that blew up in an elementary school playground in Helena on Tuesday morning. No injuries were reported, and it was not immediately clear when the blast occurred in Montana's quiet capital city.
No threat was made against Rossiter Elementary school before the exploded bomb packed in a duct tape-wrapped soda bottle was found, Lewis and Clark County Sheriff Leo Dutton said. No suspect or motive was identified.
"There's a lot of unanswered questions," Dutton said. "We're going through it methodically and slowly, so we don't miss something."
School officials discovered remnants from the detonated bomb shortly before classes began for the day, blocked off the area and called police at about 8:20 a.m., Dutton said.
No property damage was reported.
Police closed the school to search the grounds for additional devices, and thousands of students across Helena and East Helena were kept inside their schools while authorities swept for bombs outside, authorities said.
The district-wide lockdown was lifted later in the morning. "Students will be able to go outside for recess and move back and forth to music and the library," Hawthorne Elementary School principal Deb Jacobsen said in an email to parents.
Searches also were conducted at the state Capitol and government buildings, Dutton said.
Students were evacuated from the school after authorities made sure the path was clear of other devices. The children were placed on buses and sent to another location where they could be picked up by their parents, Helena public school officials said.
The FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives and the Montana Highway Patrol were assisting sheriff's and Helena police officials in the investigation.
Helena is a small city of about 30,000 people in the foothills of the Rocky Mountains. The school is in a neighborhood just north of the city's center.
This story clarifies that authorities don't know when the blast occurred, but that remnants from the explosion were found before classes began.